This invention generally relates to systems and methods for flake reduction in fibrous materials. For example, the present invention may have particular applicability in the disintegration of fiber bundles in kraft or mechanical pulps and for recycled fibers as well as in flake reduction in broke handling systems.
Turning fibrous material (e.g., lignocellulosic material) or paper (e.g., broke) into individualized fibers generally involves disintegrating fiber mats into fibers under the influence of shear in a suspension environment. This may be accomplished, for example, in a mechanical refiner between two refiner plates. The repeated application of shear in the presence of water allows the fiber mat to dissolve the fibrous compound into smaller and smaller pieces until it has broken down to the individual fiber level. At that point a suspension may be called fully “fiberized.”
The amount of time and energy used in the pulper to achieve the fully fiberized state, however, is usually prohibitive to the amount of production required of such central papermaking equipment. In reality, the prior to full fiberization. At this point, the non-fiberized parts remaining in the suspension—which are called “flakes”—are typically removed by a subsequent, specialized process. This specialized process can be faster and more efficient than pulping until fully fiberized.
This specialized process—which involves a deflaker—is known as deflaking. See, e.g., U.S. Pat. No. 3,327,952 to Rosenfeld. Deflaking describes a process where the rotary element of the deflaker turning against one or several stationary elements creates a field of hydraulic shear. This hydraulic shear may reduce the flake content of the suspension after pulping. Similar to the pulping effect there may be a need for repeated impulses on the flakes, such that the flakes may fully dissolve into singular fibers.
These pulses are generally delivered by so-called teeth on the rotor and stator plates in the deflaker, which generally either (a) pass or sweep aside each other along the generatrix of the machine similar to refiner plates (e.g., can be in the shape of a disc or a cone) or (b) intermesh in a more complicated fashion outside of the plane created by the generatrix of the machine.
The version (a) is relatively simple and may be done by refiner plates, spider web designs, or even plates consisting of holes. For example, no special requirements are needed—other than general parallelism of the contact planes between rotor and stator. Traditionally, the complex geometry of version (b) has required precision machining of the wear parts of the deflaker plates. Heretofore, this precise machining adequately solved the need for reliability and usability of these plates. But machining the plates involves higher manufacturing costs and a limit in the ability to specially design the opposing surfaces of the teeth.
That is, precision machining inherently places limits on the design of the deflaker plates. For instance, a machined deflaker plates can only have teeth in the shape of annular rings, because a lathe can only cut concentric circles into the plate. When the circles are cut, the inner and outer portions of the teeth form radians sharing the identical circle center.
Accordingly, there may exist a need in the art for a more effective configuration of deflaker plates. There may also exist a need in the art for deflaker plates that are not machined.
In an aspect, the present invention may overcome these extant deficiencies of the deflaker plate technology. For example, certain aspects of the present invention may involve the production of deflaker plates in a casting process and/or an improved design of the interfacing plate surfaces so as to facilitate improved (e.g., more efficient) deflaking.